Right now my 13 in Pacu and 6 in Silver Dollar are play mates. Even though Pacu is 7mths and the silver Dollar is 5 yrs old.
He seems to grow 2 inches a month, When I move him to a bigger tank, should I move her with him as well?
As I don't want to get another Pacu, but I don't want her to get eaten either.

I highly doubt your pacu would eat your silver dollar. Pacus are schooling fish and im sure he is trying to swim around with your silver dollar because they look similar. So if i were you i would move them together and possibly get a few more silver dollars and the pacu can be like a big goose in a school of little ducks. Now if you tried to put tetras or guppys in with the pacu you could expect those to vanish.

Right now my pacu and silver dollar are in a tank with 40 other mixed community fish. ranging from neons, tetras up to 1 six inch knife fish and 13 inch Placo. I'm torn between getting a bigger tank or finding him a nice home with his own kind.
I never thought you could get so attached to a fish.

I think the silver dollar will be fine at least for a while. Pacu will munch a fish that fits in their mouth, but they are by no means predators. Silver dollars themselves can get 8", so if you make sure it is well fed and growing all will hopefully work out.

Unfortunately, it's probably best to rehome your Pacu unless you intend a major tank upgrade. Pacu are nervous fish that are meant to be kept in groups, so it's not really fair to keep him on his own. Also, beware, they are tank busters. They are known to get scared, burst across the tank and crack the glass. You'll definitely want an acrylic tank for him.

Damn, Jo, that is a beaut! (I've heard they're really keen on Brazil nuts for food by the way). Get an indoor pond with a nice thick sheet of Lexan on one side, something in the 2000 gallon range, and put another 4 or 5 pacu and 10 or so silver dollars in there. Feed em bulk produce from Costco.

Damn, Jo, that is a beaut! (I've heard they're really keen on Brazil nuts for food by the way). Get an indoor pond with a nice thick sheet of Lexan on one side, something in the 2000 gallon range, and put another 4 or 5 pacu and 10 or so silver dollars in there. Feed em bulk produce from Costco.

But, having just reviewed some messages, that's not going to happen. Still, Beeee-yooo-tiful fish.